Answer
Interval Notation:
$(-\infty, 0]$.
Inequality Form:
$x \le 0$.
Work Step by Step
The graph involves an open bracket.
This means that the number where the bracket is located is included in the interval.
The graph goes to the left of $0$ without bound.
This means that the lower limit is $-\infty$.
The graph covers all the numbers to the left of, and including $0$.
This means that the interval is $(-\infty, 0]$.
The inequality equivalent of this is $x \le 0$.